First of all, cash is rarely used in Sweden today. It used to be only the royal family don't carrying cash, today very few people use it. Even older people opt for electronic payment to diminish the risk of theft.

The two prominent payments are various cards (such as Mastercard) or Swich. You're probably wondering, what on earth that is. Swich is a app set up by the banks. Throught your bank you connect your mobile phone number to your bank account. You sign each transfer with your electronic bank-ID (that can used to sign a lot of other stuff as well). Swich is mainly used for smaller sums. The beauty of it is that you can make an instant transfer to a private person or a business, facilitating e.g. splitting a restaurant bill or buying a single ticket on e.g. busses. In the series we see an edited version of this in S1:E4 when August finally pays Simon. And it looks like Sara is using Swish in the school café in S2:E1, although Stella seems to pay with card (there is an izettle tool on the desk).

Many travel app:s offers the option to pay by a connect card or by Swish, like in S1 when Wille takes the bus to Bjärstad.

Invoices (like the one Simon got for his tutorial session) is payed via bank transfer, or rather to a special business payment account called bankgiro.